1. Field of the Invention
The present invention relates to a fluid pressure booster for a braking device, including: a control piston on which an input brake operation acts in an advancing direction, and a reaction force based on fluid pressure of a booster fluid pressure generation chamber that generates fluid pressure for actuating a master piston of a master cylinder acts in a retracting direction; a pressure increasing valve that has at least a cylindrical valve seat member which is provided, at a front end thereof, with a valve seat facing a valve chamber communicating with a fluid pressure generation source, a valve body that is urged by a spring toward a side where the valve body is seated on the valve seat and is housed in the valve chamber, and a pressing rod that is coaxially inserted in the valve seat member to be able to push the valve body with the front end so that the valve body is separated from the valve seat, opens according to the advance of the control piston, and is provided between the valve chamber and the booster fluid pressure generation chamber; and a pressure reducing valve provided between a release chamber communicating with a reservoir and the booster fluid pressure generation chamber to close at a time of advance of the control piston and open at a time of retraction of the control piston.
2. Description of the Related Art
According to, for example, Japanese Patent Application Laid-open No 2009-234525, a fluid pressure booster for a braking device is already known, which is configured such that at least part of a pressure increasing valve presses a valve body using a pressing rod that advances according to the input brake operation to separate the valve body from a valve seat at a front end of a cylindrical valve seat member to open the valve.
However, at an early stage of opening of the pressure increasing valve, a large fluid pressure difference occurs between the fluid pressure generation source and the booster fluid pressure generation chamber. When an abrupt fluid pressure flow occurs based on the fluid pressure difference at the early stage of opening of the pressure increasing valve, the working sound thereof is likely to be sensed and/or heard as an abnormal sound.